(1) Field of the Invention
The present invention relates to a method of producing a polymer from an ethylenically unsaturated organic monomer. More particularly, the present invention relates to a method of producing a polymer by a catalytic addition-polymerization of an ethylenically unsaturated organic compound, for example, an olefin compound, a vinyl compound and a conjugated diene compound, particularly 1,3-butadiene, in which method hydrogen is utilized as a molecular weight-modifier.
(2) Description of the Related Art
It is well-known that conjugated diene compounds, for example, 1,3-butadiene can be polymerized in the presence of catalysts to produce various types of corresponding polymers different in microstructure thereof from each other, in response to the types and compositions of the catalysts used for the polymerization.
In view of micro structure of the polybutadiene, when 1,3-butadiene is polymerized at the 1- and 4-positions of the molecule thereof, a 1,4-structure is formed in the resultant polymeric chain, and when 1,3-butadiene is polymerized at the 1- and 2-positions of the molecule thereof, a 1,2-structure is formed in the resultant polymeric chain.
The polymeric chain of the polybutadiene usually contains both the 1,4-structure and the 1,2-structure. The 1,4-structure includes a cis-1,4-structure and a trans-1,4-structure. The 1,2-structure forms a vinyl side chain in the molecule of the polybutadiene.
As mentioned above, various types of polybutadienes different in the above-mentioned micro structure from each other can be produced in response to the type and composition of the catalyst used. The difference in the micro structure causes a difference in physical and mechanical properties of the resultant polymer. The various types of polybutadiene can be employed in various uses in response to the properties thereof. For example, a certain type of polybutadiene having a high linearity in the molecule thereof exhibits excellent resistance to abrasion and resistance to heat generation and a superior impact resilience.
Further, it is known that a polybutadiene having a high cis-structure content can be produced in the presence of a catalyst comprising a cobalt compound and an organic aluminum compound, and it is expected that a polybutadiene having an appropriate content of a 1,2-structure in combination with the high content of cis-structure is useful as an impact resistance-imparting agent for aromatic vinyl polymers.
Currently, various types of polymerization methods for olefin compounds using a metallocene complex as a catalyst are being briskly developed, and the polymerization of the conjugated diene compound in the presence of the metallocene catalyst is also being studied.
Concerning the polymerization of the conjugated diene compound in the presence of the metallocene complex as a catalyst, Macromol. Symp. 89, 383 (1995) discloses a catalyst system comprising a compound of transition metals of Group IV of the Periodic Table, such as cyclopentadienyl titanium trichloride (Cp TiCl3) and methyl alumoxane. This catalyst is disadvantageous in a low catalytic activity for polymerization for the conjugated diene compounds.
Japanese Examined Patent Publication No. 46-20,494 discloses a method of producing a polybutadiene using a catalyst system comprising CpVCl3, (i-C4H9)3Al/AlCl3 and H2O. This catalyst system is disadvantageous in a low catalystic activity for polymerization of butadiene.
Polymer Vol. 37 (2), p. 363 (1996) reports a method of producing polybutadiene having 10 to 20% by mole of 1,2-structure in combination with a high cis-structure in the presence of a catalyst comprising a vanadium (III) compound, for example, CpVCl2(PEt3)2 or Cp2VCl, which is a metallocene complex of a transition metal of Group V of the Periodic Table, and methyl alumoxane.
Japanese Unexamined Patent Publication No. 9-194,526 disclose methods of producing a polybutadiene in the presence of a combination of a vanadium metallocene compound having a specific structure and an ionization agent.
As a method of controlling a molecular weight of polybutadiene during a polymerization procedure of 1,3-butadiene, for example, in a production procedure of a high cis-structure polybutadiene in the presence of a catalyst comprising a cobalt compound or a nickel compound and an organic aluminum compound. Japanese Examined Patent Publication No. 41-5,474 discloses a method using cyclooctadiene as a molecular weight modifier for the polybutadiene. This method is, however, disadvantageous in that when cyclooctadiene is added to a polymerization system containing a catalyst containing a metallocene complex of transition metals of Group V of the Periodic Table, the catalytic activity of the catalyst for polymerization decreases and/or the micro structure of the polymer of the conjugated diene compound changes.
U.S. Pat. No. 6,300,450 discloses that in a polymerization of a conjugated diene compound in the presence of a catalyst comprising a metallocene complex of compounds of transition metals of Group V of the Periodic Table, the molecular weight of the resultant polymer of the conjugated diene compound is controlled by carrying out the polymerization in the presence of hydrogen.
In this method, however, since the hydrogen is directly introduced into the polymerization mixture in a polymerization vessel, when the viscosity of the polymerization mixture (liquid) increases, the distribution of hydrogen in the polymerization mixture in the polymerization vessel may become uneven and the contiol of the molecular weight may be unstably effected. Accordingly, this method should be improved.
As disclosed in U.S. Pat. No. 6,071,845, the inventors of the present invention found that when a polymerization catalyst comprising a metallocene complex of vanadium metal compounds and an ionic compound of non-coordinated anionic compound with cationic compounds and/or aluminoxane is used for polymerization of 1,3-butadiene, the resultant product is a polybutadiene (MBR) having a micro structure in which an appropriate content of 1,2-structure is combined with cis-1,4-structure in a high content and trans-1,4-structure in a low content, and a high molecular linearity. This polybutadiene resin exhibit excellent properties, and thus various attemps have been made for applications of the polybutadiene resin for high impact strength polystyrene resins and tire materials. However, the polybutadiene resin exhibits a relatively high cold flow and thus, sometimes, should be improved in aptitude to storage and transportation.
Japanese Unexamined Patent Publication No. 11-236,411 discloses a polybutadiene resin (MBR) exhibiting a molecular weight distribution having two peaks. This MBR resin comprises a low molecular weight fraction has a weight average molecular weight of 2000 to 300,000 and a high molecular weight fraction having a weight average molecular weight of 500,000 to 5,000,000. In the examples of the Japanese patent publication, two peak type polybutadiene resins each comprising a high molecular weight fraction having a weight average molecular weight similar to that of usual butadiene rubber, for example, 350,000 to 600,000, and a very low molecular weight fraction are disclosed. However, this Japanese patent publication is quite silent as to an improvement of the cold flow property of the two peak type polybutadiene resins.
An object of the present invention is to provide a method of producing a polymer from at least one ethylenically unsaturated organic monomer, in which method the molecular weight of the target polymer is smoothly controlled by using hydrogen as a molecular weight modifier.
Another object of the present invention is to provide a method of producing a polymer from at least one ethylenically unsaturated organic monomer, in which method the molecular weight of the target polymer is smoothly controlled by using hydrogen as a molecular weight modifier and the target polymer is continuously produced with high conversion of the monomer, efficiency and productivity.
The above-mentioned objects can be attained by the method of the present invention for producing a polymer from at least one ethylenically unsaturated organic monomer, which method comprises
(1) bringing, in a mixing vessel, a hydrogen-containing gas into contact with an inert organic solvent, to prepare a solution of hydrogen in an inert organic solvent, in which solution, a vapor-liquid phase equilibrium between the vapor phase hydrogen in the hydrogen-containing gas and the liquid phase hydrogen in the solution is attained;
(2) addition-polymerizing, in a reactor consisting of at least one reaction vessel, at least one ethylenically unsaturated organic monomer having at least one ethylenical double bond in the presence of a catalyst in the solution of hydrogen in the inert organic solvent, to thereby produce a polymer of the ethylenically unsaturated organic monomer, while controlling the molecular weight of the polymer in the presence of hydrogen dissolved in the inert organic solvent.
In the polymer-producing method of the present invention, the ethylenically unsaturated organic monomer is preferably selected from the group consisting of non-cyclic monoolefines, cyclic monoolefins, conjugated diene monomers, aromatic vinyl compounds, and non-conjugated diolefin compounds.
In the polymer-producing method of the present invention, the conjugated diene monomers are preferably selected from the group consisting of 1,3-butadiene, isoprene, 1,3-pentadiene, 2-ethyl-1,3-butadiene, 2,3-dimethylbutadiene, 2-mehylpentadiene, 4-mehtylpentadiene, and 2,4-hexadiene.
In the polymer-producing method of the present invention, the inert organic solvent preferably comprises at least one member selected from aromatic hydrocarbons having 6 to 12 carbon atoms, aliphatic saturated hydrocarbons having 4 to 12 carbon atoms, olefinic hydrocarbons having 2 to 12 carbon atoms, halogenated hydrobarbons, mmineral spirits, solvent naphtha and kerosine.
In the polymer-producing method of the present invention, preferably the hydrogen-containing gas fed into the mixing vessel has a partial pressure of hydrogen of 0.0001 to 3 MPa at a temperature of xe2x88x9210 to +90xc2x0 C., and the content of hydrogen in the inert organic solvent solution is adjusted to 0.1 to 50 ppm by mass.
In the polymer-producing method of the present invention, in the addition-polymerization step, hydrogen present in the inert organic solvent solution is preferably in an amount of 0.01 to 500 milli moles, per mole of the ethylenically unsaturated organic monomer.
In the polymer-producing method of the present invention, the addition polymerization is preferably carried out at a temperature of xe2x88x92100 to 120xc2x0 C.
In the polymer-producing method of the present invention, preferably the catalyst comprises;
(A) a metallocene complex of a transition metal compound,
(B) an ionic compound produced by a reaction of a non-coordination anionic compound with a cationic compound, and
(C) an organic metal compound of an element of groups I to III of the Periodic Table, and optionally
(D) water.
In the polymer-producing method of the present invention, the addition polymerization reaction of the ethylenically unsaturated organic monomer is carried out optionally in the presence of a chain-transfer agent.
In an embodiment of the polymer-producing method of the present invention, the ethylenically unsaturated organic monomer is 1,3-butadiene, the catalyst comprises (a) a metallocene complex of a transition metal compound and (b) at least one member selected from the group consisting of (i) an ionic compound produced by a reaction of a non-coordination anionic compound with a cationic compound, and (ii) an aluminoxane compound; and the resultant polybutadiene resin comprises (I) a lower molecular weight polybutadiene fraction having a weight average molecular weight (Mw) of 305,000 to 700,000, determined by using a gel permeation chromatograph (GPC) and (II) a higher molecular weight polybutadiene fraction having a weight average molecular weight (Mw) of 1,000,000 to 10,000,000, determined by using a gel permeation chromatograph (GPC), each fraction having a molar content of 1,2-structure of 4 to 30%, a molar content of cis-1,4-structure of 65 to 95% and a molar content of trans-1,4-structure of 5% or less.
In the above-mentioned embodiment of the polymer-producing method of the present invention, the polybutadiene fraction (II) is preferably in a content of 0.01 to 50% by mass on the basis of the total mass of the polybutadiene resin.
In the above-mentioned embodiment of the polymer-producing method of the present invention, preferably the addition polymerization reaction of 1,3-butadiene is carried out in the presence of a chain transfer agent, and the lower molecular weight fraction (I) and the higher molecular weight fraction (II) of the polybutadiene are successively produced by chaining the content of the chain transfer agent in the reaction system.
In the above-mentioned embodiment of the polymer-producing method of the present invention, preferably, the addition polymerization reaction of 1,3-butadiene is continuously, carried out in a reactor comprising a first reaction vessel connected in series to a second reaction vessel and the lower molecular polybutadiene fraction (I) is mainly produced in the first reaction vessel and then the higher molecular polybutadiene fraction (II) is mainly produced in the second reaction vessel.
In the above-mentioned embodiment of the polymer-producing method of the present invention, the content of the higher molecular weight polybutadiene fraction (II) in the resultant polybutadiene resin is preferably controlled by adding a polymerization stopper to the reaction system is the second reaction vessel.
In the polymer-producing method of the present invention, in the hydrogen solution-preparing step (1) in the mixing vessel, optionally the hydrogen-containing gas is brought into contact with an inert organic solvent having been mixed with at least one ethylenically unsaturated organic monomer and a catalyst, and after the vapor-liquid phase equilibrium is attained between the vapor phase hydrogen in the hydrogen-containing gas and the liquid phase hydrogen in the solution, the resultant liquid mixture is introduced from the mixing vessel into the reactor.